Source, dynamics, and risks of microplastics and nanoplastics in agricultural groundwater systems

CARPANEZ, THAIS G.; CASTRO, LIVIA MARIA C.; SANTOS, CAROLINA R. DOS; AMARAL, MÍRIAM CRISTINA S.; MOREIRA, VICTOR R.

doi:10.1590/0001-3765202420241393

Abstract

Micro- and nanoplastics (MNPs) are emerging contaminants increasingly recognized for their environmental and health implications. While surface water systems have been extensively studied, the presence, behavior, and impacts of MNPs in groundwater remain underexplored, despite its critical role as water source worldwide. The findings in this review highlight that agricultural activities, particularly plastic mulches, pesticides containers, fertilizer bags, greenhouses, are major sources of MNP. Nanoplastics, predominant in groundwater due to their enhanced mobility in the vadose zone, exhibit a higher sorption capacity, facilitating the transport and accumulation of toxic substances such as hydrophobic organic pollutants and trace metals to/in groundwater. The review also discusses the hydrogeological and environmental factors influencing micro(nano)plastics distribution. In complement, synergistic and antagonistic effects arising from MNP interactions with other contaminants were reviewed, emphasizing the interactions with contaminants derived from agricultural practices (nitrate, herbicides, pesticides, and salts). Despite the generally low concentrations of MNPs in groundwater, their seasonal variability, combined with the aging of particles, underscores the need for long-term monitoring and risk assessments specific to groundwater systems. These findings reinforce the importance of research that addresses the unique challenges posed by micro- and nanoplastics in groundwater systems, ensuring their environmental protection.

Key words
agriculture and pollution; environmental contamination; vertical mobility; microplastics migration

INTRODUCTION

Agricultural activities are essential to ensuring food security and supporting economies worldwide. However, they often come with significant environmental costs, particularly affecting soil and groundwater resources. Groundwater, which provides nearly half of the world’s drinking water and is a critical resource for agricultural irrigation, is increasingly under threat from various forms of contamination (Jasechko & Perrone 2021). Among the well-documented impacts of agriculture on groundwater quality are nitrate leaching from fertilizers (Abascal et al. 2022), pesticide infiltration (Araya et al. 2024), and the introduction of other trace organic pollutants (Pinasseau et al. 2020). These contaminants are known to compromise water quality, posing risks to both human health and aquatic ecosystems.

In recent years, the focus has expanded to include emerging contaminants such as microplastics, whose presence in groundwater systems remains less explored but equally concerning. Microplastics—defined as plastic particles smaller than 5 mm—are introduced into agricultural environments through diverse sources, including plastic mulching films, irrigation pipes, fertilizer bags, and pesticide containers (Tian et al. 2022). Over time, these plastics fragment into smaller particles under environmental conditions, becoming ubiquitous contaminants in soils and potentially infiltrating groundwater. While microplastics are a growing environmental concern, research indicates that nanoplastics—particles smaller than 1 µm—may pose even greater risks (Nath et al. 2024, Liu et al. 2021). Due to their diminutive size, nanoplastics exhibit enhanced mobility, enabling them to traverse soil and rock strata and penetrate deeper into aquifers. Their ability to bypass natural filtration mechanisms raises alarms about their potential to contaminate groundwater systems.

The ecological and health impacts of nanoplastics are more profound compared to larger microplastics. Nanoplastics have a larger surface-area-to-volume ratio, which enhances their reactivity and ability to adsorb and transport other harmful substances, such as pesticides, antibiotics, and heavy metals (Cai et al. 2021, Shi et al. 2024). Furthermore, their small size makes them more bioavailable to organisms, increasing the likelihood of ingestion and subsequent entry into food chains (Li et al. 2023, Slaveykova & Marelja 2023). Despite these concerns, the presence, sources, and fate of nanoplastics in groundwater remain understudied, leaving significant gaps in our understanding of their environmental implications.

This article aims to bridge these gaps by reviewing the current state of knowledge on micro- and nanoplastic contamination in groundwater. The review explores the pathways through which these particles enter groundwater systems, including vertical infiltration through soils, atmospheric deposition into soils followed by vertical infiltration, and contamination from surface water interaction. Additionally, it examines the role of agricultural practices in amplifying these contamination pathways and highlights the unique challenges posed by nanoplastics in terms of detection, mobility, and toxicity. While existing studies provide valuable insights, their findings often diverge, underscoring the need for a consolidated synthesis of the available information. Summarizing these varying perspectives is crucial for identifying actionable steps to advance discussions and address persistent knowledge gaps in this evolving field.

Search strategy and selection criteria

A systematic literature search was conducted using the Web of Science and ScienceDirect databases. Over 50 articles published since 2019 – 2024 (5-year time frame) were selected based on a combination of keywords, including (“microplastics” OR “nanoplastics”) AND (“groundwater”) AND (“agricultural areas”) AND (“physical properties” OR “contaminant interaction” OR “microbial impact”). The following keywords were used to select studies discussing toxicity: (“microplastics” OR “nanoplastics”) AND (“groundwater”) AND (“agricultural areas”) AND (“toxicity”) AND (“nitrate” OR “salinity” OR “phosphate” or “pesticides and herbicides”). The selection process prioritized articles from journals with higher impact factors to ensure the relevance and quality of the sources. Theses, dissertations, book chapters, and books were excluded to maintain a high standard of evidence and relevance. The fields that contributed to more than 80% of the total articles included environmental science, chemical engineering, and agricultural and biological science. The search strategy used in this study was illustrated in Figure 1.

Figure 1
Search strategy used in this study, illustrating the Boolean equation applied across selected databases.

By addressing these critical aspects, this review provides an updated framework for understanding the intersection of agricultural practices and plastic pollution in groundwater systems. The discussions and data presented here specifically focus on groundwater in proximity to agricultural activities, distinguishing this work from other studies with a broader perspective on the occurrence of micro- and nanoplastics in groundwater. The findings aim to inform sustainable agricultural and water management practices, contributing to the broader efforts to mitigate emerging contaminants in vital water resources.

MICRO(NANO)PLASTICS IN AGRICULTURAL GROUNDWATER SYSTEMS

Groundwater contamination by micro- and nanoplastics has emerged as a pressing environmental concern, closely tied to diverse land use practices. Studies have shown that land use significantly influences the abundance and characteristics of microplastics particles in groundwater, reflecting varying contamination sources and mechanism. For instance, the concentration of plastic particle exhibit a high coefficient of variation (883.5%) across different land use types, with values reported as 17.5 MP/L in nature reserves, 13.4 MP/L in landfills, 4.2 MP/L in industrial areas, 3.0 MP/L in residential zones, and 1.0 MP/L in agricultural regions (He et al. 2024). Although higher concentrations of microplastics were reported in samples from natural reserves, this finding is likely attributable to the inclusion of coastal sampling sites subject to anthropogenic influence from recreational activities and marine currents, rather than the absence of land use controls. He et al. (2024) highlighted that there is a greater accumulation of plastic in coastal areas due to human recreation and marine current movements. This has already been verified by other authors when evaluating the presence of MPs in sediments and surface water in coastal areas of natural reserves (Machendiranathan et al. 2024, Gong et al. 2023).

Specifically for groundwater systems, Figure 2 summarizes the data on plastic particles concentration, format and polymers that were found. Complementary information was provided in Supplementary Material - Table SI. Notably, the concentration of microplastics varies. The relatively low concentrations of microplastics reported for some regions have been linked to minimal soil amendments (e.g.: biosolids) and fertilizers application and no report on localized pollutant sources. However, the variability of data suggests that agricultural practices can also significantly contribute to groundwater contamination under different conditions. Specifically for agricultural areas, the following represent important sources of micro- and nanoplastics inputs, including plastic mulches, pesticides containers, fertilizer bags, greenhouses, and other plastic-based materials (Jeong et al. 2023). Among these, plastic mulching films are often identifying as a dominant source, with their widespread usage and degradation processes introducing substantial amounts of microplastics into soil and groundwater systems (Huang et al. 2020, Feng et al. 2021, Jeong et al. 2023).

Figure 2
Concentration (n=203), formats (n=291), and polymers (n=532) found in groundwaters affected by agricultural activities. Citations are provided in Supplementary Material - Table SI.

Vertical infiltration through soil is a major mechanism by which micro- and nanoplastics enter groundwater. Soil and rock pores act as natural filters, allowing selective particle transport based on size and density. This process tends to favor the movement of smaller particles, such as nanoplastics, which can penetrate deeper into aquifers. Studies have shown that larger particles are more likely to be retained in shallower wells, where filtration processes are less intense, while smaller particles dominate in deeper reservoirs (Viaroli et al. 2022, He et al. 2024). The role of soil as compartment that accumulates larger microplastics further supports the hypothesis that particle size degradation enhances vertical mobility and contributes to nanoplastics presence in groundwater.

Invisible sources of pollution, such as wear from agricultural machinery, atmospheric deposition, and surface runoff, also contribute significantly to groundwater contamination. In a study presented by Cha et al. (2023) polypropylene (PP) and polyethylene (PE) were detected in 95% of groundwater samples, with PP unexpectedly predominating (~75%), despite PE being the primary polymer in agricultural mulches. This discrepancy has been attributed to the greater resistance of PP to environmental degradation compared to PE, in addition to supplementary PP sources such as abrasion from agricultural machinery and atmospheric deposition. These factors may enhance the environmental persistence and prevalence of PP in groundwater samples.

Atmospheric deposition, both dry and wet, has been highlighted as another critical pathway for microplastic contamination. Research in karst swamp regions found elevated microplastic concentrations in open wells compared to closed systems, with road dust and textile fibers identified as major sources (Wei et al. 2024). The potential for long-distance atmospheric transport of microplastics, combined with localized deposition patterns, underscores the complexity of contamination dynamics in groundwater systems.

Surface water intrusion and the use of reclaimed water for aquifer recharge further complicate the scenario. Microplastics contamination in surface water bodies often mirrors that of adjacent groundwater systems in terms of polymer types (e.g.: PP, PE, and polystyrene (PS)) and particle sizes, indicating a bidirectional exchange of contaminants (Gündoğdu et al. 2023, Shu et al. 2023). While aquifer recharge using treated water can mitigate drought impacts, inadequate treatment may introduce micro- and nanoplastics and associated pollutants, posing risks to groundwater quality.

In analyzing the formats of particles found in groundwater, fiber represent the largest fraction, totaling 45% (Figure 2). Fragments are the second most prevalent format, accounting for 39% of the particles. These typically originate from the degradation of other particles, being byproducts of mechanical and chemical degradation processes. Films and pellets were found in smaller proportions. For the polymers, the data shows a dominance of PE, PP and polyethylene terephthalate (PET). The chemical resistance of polyethylene can prolong its environmental presence, whereas the lower density of polypropylene facilitates its flotation in aquatic environments and accumulation near the sampling points. Other polymers such as polyvinyl chloride (PVC) and PS are present in smaller proportions.

The analysis of particle sizes (Figure 3) highlights a distinctive pattern for groundwater compared to other environmental matrices. In groundwater samples, the average particle size is 744 ± 1367 nm, significantly smaller than the sizes observed for biosolids and soil. This trend points to a predominance of smaller particles, including nanoplastics, in the subsurface environment (Mu et al. 2022). This also raises concerns about secondary contamination of soil and plants during irrigation with groundwater containing nanoplastics. There is recent concern about the reintroduction of microplastics into the environment through the agricultural use of biosolids from wastewater treatment plants, in which the presence of microplastics has already been evidenced (Kwiatkowska & Ormaniec 2024, Hassan et al. 2023). However, irrigation with groundwater contaminated with nanoplastics could be an additional and even more dangerous source of reintroduction of these pollutants into the environment since plastic nanoparticles may have higher hazards, challenging detection and removal, and environmental persistence compared to microparticles, as will be discussed in the following sections.

Figure 3
Comparison of particle size distributions across different environmental matrices and groundwater systems. Details on the sources of groundwater data are provided in Supplementary Material - Table SI. While particle size data for biosolids, soil, and wastewater are not included in this study, they are available upon request.

HYDROGEOLOGICAL AND ENVIRONMENTAL INFLUENCING MICRO(NANO)PLASTICS DISTRIBUTION

The distribution and concentration of micro- and nanoplastics in groundwater systems nearby agricultural areas are influenced by a complex interplay of environmental, geological, and hydrogeological factors. Seasonality is a first factor being presented and dictates the occurrence and variability in concentration. Cha et al. (2024) observed that during the dry season, lower concentrations of particles were recorded, with larger particles being more predominant. Conversely, in the rainy season, higher concentrations of particles were observed, with smaller particles prevailing. This seasonal variation likely results from increased infiltration of micro- and nanoplastics during heavy rainfall, which facilitates the transport of particles from the soil surface into groundwater systems. Additionally, increased groundwater usage in surrounding areas during the rainy season may contribute to the heightened prevalence of smaller particles through redistribution mechanism.

However, contrasting evidence complicates this understanding. For instance, Cha et al. (2023) reported higher particle concentrations during the dry season, ranging from 0.20 – 3.48 MP/L (mean: 1.15 MP/L; median: 0.83 MP/L), compared to the rainy season. It was suggested that heavy rainfall during the wet season could lead to dilution effects, reducing microplastic concentrations in groundwater. Notably, although the mean concentrations were higher during the dry season (1.15 MP/L) compared to the rainy season (0.64 MP/L), statistical analysis revealed no significant difference between the medians (p=0.2147). These findings highlight the spatial and temporal heterogeneity of plastic particles dynamics in groundwater systems, which are further influenced by local hydrogeological conditions. These divergent trends underscore the need for region-specific and temporally resolved studies that account for hydrogeological variability, rainfall intensity, and land use, to clarify the seasonal dynamics of microplastic infiltration into groundwater.

The vadose zone, often acting as a filtration barrier, plays an important role in limiting the vertical penetration of micro- and nanoplastics. In general, its efficiency as a filtration barrier is highly dependent on soil texture, structure, and porosity. Sandy soils, with larger pore spaces, may facilitate faster vertical migration of nanoplastics compared to clay-rich layers, which offer greater resistance due to smaller pores and higher sorption capacity. The literature also has some considerations about these aspects.

About its role as barrier to micro- and nanoplastic barrier, O’Connor et al. (2019) and Jeong et al. (2023) noted that despite increased precipitation, the penetration depth of micro- and nanoplastics into the vadose zone remained relatively unchanged, underscoring the effectiveness of this layer in mitigating downward migration. Nevertheless, the role of the vadose zone is not absolute, as factors like soil porosity, particle size and polymer density can mediate infiltration dynamics. For example, Samandra et al. (2022) observed consistent seasonal differences in microplastic concentrations with higher abundance during the dry season (21 to 513 particles) compared to the wet season (7 to 272 particles). These differences, confirmed by the Wilcoxon ran-sum test (p< 0.05) reflect the complex interactions between rainfall intensity, soil retention capacity, and hydrological flow pathways. Regardless of the season, Wei et al. (2024) highlight that small-sized microplastics (<1 mm) dominate in the groundwater. However, the proportion of small-sized microplastics is higher during the rainy season compared to the dry season.

Particle size and morphology also exhibit significant spatial variations influenced by hydrodynamic processes. Wei et al. (2024) demonstrated that groundwater flow regimes impact the characteristics of micro- and nanoplastics between upstream and downstream sections. In downstream locations, the diversity of particle colors increased, while the proportion of fragments decreased from 50.8% upstream to 30.5% downstream (p<0.05). Conversely, the percentage of pellets increased downstream, suggesting particles sorting during transport. Fiber proportions remained relatively constant, likely due to their flexibility and resistance to fragmentation. Polymer composition also varied, with a reduction in PP and PE and an increase in polyamide (PA) downstream, although these trends were not statistically significant. These findings suggest that groundwater flow regimes not only affect the distribution of particles but also modify their morphological and compositional attributes over distance.

Polymer density is another critical determinant of microplastic distribution (Ren et al. 2021). Denser polymers, such as PET (1.38 – 1.41 g/cm³) and polyurethane (PU) (1.2 – 1.26 g/cm³), tend to migrate more effectively through soil layers compared to lighter polymers. Mu et al. (2022) reported predominance of PET (39 – 6009 MP/L) and PU (3-165 MP/L) in groundwater, aligned with their higher densities and enhanced vertical migration capabilities. These findings underscore the role of material properties in shaping the transport and retention of plastic particles in subsurface environments.

Longitudinal flow further influences micro- and nanoplastics distribution, as observed in studies examining downstream concentrations. He et al. (2024) documented a general trend of higher particle concentrations downstream in groundwater systems spanning distances over 10 km. However, in regions characterized by topographical heterogeneity, such as valleys and peaks, micro- and nanoplastics tend to accumulate during the dry season due to reduced hydraulic flow (Wei et al. 2024). Moreover, smaller microplastics are more susceptible to surface runoff and interflow, which can facilitate their transport to groundwater through infiltration pathways.

Hydrogeological parameters, including groundwater properties, also influence micro- and nanoplastics behavior. While parameters such as pH (6.5 – 7.6) and dissolved oxygen (1.0 – 1.7 mg/L) typically show minimal variation in groundwater systems (Alvarado-Zambrano et al. 2023), other factors, such as temperature, can play a more significant role. For example, temperature variations (28.2 – 31.7C °C) were found to correlate with micro- and nanoplastics distribution, suggesting temperature-dependent physicochemical interactions. Additionally, correlations between microplastics and suspended solids, total organic carbon (Cha et al. 2023, 2024), and water velocity (An et al. 2022) further emphasize the influence of groundwater flow dynamics on particle transport.

Topographical and hydrogeological factors also affect microplastic distribution, as reflected in correlations between their concentration and groundwater level (r = -0.48, p < 0.05), topographic elevation (r = -0.59, p < 0.05), and distance from the sea (r = -0.67, p < 0.05) (Kim et al. 2023). These correlations suggest that proximity to contamination sources, such as coastal areas or agricultural regions, plays a crucial role in determining microplastic prevalence. Moreover, positive correlations between microplastic abundance and environmental parameters, such as turbidity (r = 0.93, p ≤ 0.05) and chloride concentration (r = 0.88, p ≤ 0.05), indicate the potential contribution of marine intrusion and swamp-derived contamination (Alvarado-Zambrano et al. 2023).

Finally, groundwater ion composition, though less directly studied in relation to microplastics, has shown significant correlations with specific ions such as Ca²⁺, K⁺, Mg²⁺, SO₄²⁻, and HCO₃⁻ (Jeong et al. 2023). In agricultural areas, the presence of NO₃⁻ further correlates with microplastics (r = 0.45), reflecting the combined influence of anthropogenic activities and natural groundwater chemistry. These findings highlight the multifaceted nature of microplastic distribution and the need for comprehensive investigations that integrate hydrogeological, chemical, and environmental perspectives.

Additionally, methodological standardization remains critical. Variations in sampling and analytical techniques can introduce significant biases, emphasizing the importance of establishing standardized protocols for micro- and nanoplastic studies in groundwater to ensure data comparability across regions and studies. For smaller sampled volumes (100 L), Cha et al. (2024) found lower concentrations of particles and a predominance of smaller particles compared to larger volumes sampled (500 L). This suggests a potential superficial accumulation of smaller particles in groundwater. As water is extracted, the concentration of MPs decreases, while the proportion of larger particles increases.

These observations regarding the occurrence of plastic particles in groundwater are summarized in Figure 4, which outlines the various factors influencing the presence of micro- and nanoplastics in groundwater.

Figure 4
Comparison of particle size distributions across different environmental matrices and groundwater systems. Details on the sources of groundwater data are provided in Supplementary Material - Table SI. While particle size data for biosolids, soil, and wastewater are not included in this study, they are available upon request.

MPS INTERACTION WITH ORGANISMS AND TOXICITY

The toxicity of micro- and nanoplastics in groundwater remains an underexplored yet critical research area. Current studies emphasize significant gaps in understanding the toxicological impacts of these materials, particularly nanoplastics, for which toxicity data is even scarcer (Pencik et al. 2023). Factors such as particle concentration, exposure duration, polymer composition, shape, size, origin, aging processes, and their sorptive interactions with other contaminants are pivotal variables influencing toxicity outcomes. These variables, as recommended by Pencik et al. (2023), align with broader observations in the literature, which individually examine these aspects to elucidate their contributions to toxicological effects.

For groundwater, where agricultural activities are often a major source of contamination, the interplay between micro- and nanoplastics and coexisting pollutants like nitrates, pesticides, herbicides, phosphorus, and salts is particularly concerning. This coexistence may exacerbate or mitigate toxic effects depending on synergistic or antagonistic interactions between the pollutants, as illustrated in Figure 5. However, the limited number of studies examining these interactions in groundwater systems—especially those investigating the combined effects of multiple contaminants under varying conditions such as pH, redox potential, and organic matter content—highlights an urgent need for more specialized research.

Figure 5
Dynamics of micro- and nanoplastics in groundwaters affected by agricultural activities.

Notably in Figure 5, two classes of contaminants stand out in the context of groundwater contamination, which are pesticides and salinity. Pesticides, specifically, lipophobic pesticides, such as organochlorines, and herbicides can efficiently adsorb onto the surfaces of microplastics, enhancing their persistence in the environment and, consequently, increasing the exposure of aquatic organisms to toxic concentrations (Li et al. 2021). Given the anaerobic or microaerophiles conditions commonly observed in groundwater, these interactions may manifest differently compared to surface waters, potentially affecting microbial metabolic pathways or the persistence of bound contaminants.

There are still long-term concerns regarding the presence of these micro- and nanoplastics, as has been demonstrated by Zeng et al. (2024) that the sorption capacity of pesticides and herbicides tends to increase as the particles age, indicating the potential for compound accumulation over time. In addition, it is important to highlight that nanoplastics, predominant in groundwater, exhibit an even higher sorption potential compared to microplastics. This is due to their increased surface area, which allows them to bind a larger number of contaminants (Yu et al. 2019).

Salinity, another often overlooked aspect in the contamination of groundwater by microplastics, also plays a crucial role in toxicity. In saline environments, the interaction between microplastics and contaminants like heavy metals, pesticides, or even nutrients like phosphorus can be intensified due to the greater affinity of microplastics for these compounds in saline solutions (Puckowski et al. 2021, Guo et al. 2019, Atugoda et al. 2020, Stapleton et al. 2023).This can represent an additional contribution to the risk of bioaccumulation and amplify toxic effects on organisms living in these groundwater environments, making it essential to conduct more detailed studies of the specific conditions that characterize these ecosystems and their interactions with microplastics and agricultural contaminants.

Comparing groundwater to surface water systems, the latter, particularly freshwater and marine environments, have received far greater attention in microplastic toxicity studies (Pencik et al. 2023). Surface waters, for instance, exhibit higher contaminant loads, more dynamic interactions with biological communities, and greater microplastic concentrations, creating a well-documented arena for studying these materials’ impacts. Marine systems, in particular, have advanced the understanding of microplastic interactions with heavy metals, persistent organic pollutants, and marine organisms, demonstrating their role as vectors for toxic substances.

Groundwater systems, however, present distinct challenges: lower oxygen levels, reduced microbial diversity, and slower contaminant transport rates—all of which potentially influencing the fate and toxicity of micro- and nanoplastics differently from surface waters. These inherent differences in water chemistry and flow dynamics underscore the need for groundwater-specific studies to assess the ecological risks accurately.

FUTURE PERSPECTIVES

Agriculture plays an important role in sustaining global food security, but it is also a major contributor to environmental challenges, including groundwater contamination. It is recognized that the widespread use of plastic-based materials in agricultural areas has contributed to micro- and nanoplastics (MNPs) into subsurface water systems. Even so, the study of MNPs in regions influenced by agricultural activities is still in its beginnings. The unique hydrogeological characteristics of groundwater systems and the distinct pathways in which MNPs enter and are transported in these environments demand specific and target research. Future investigations should, therefore, address the temporal variation, mechanistic studies on MNP interactions with agricultural contaminants, ecotoxicological assessments in groundwater ecosystems, modeling the fate and transport of MNPs in subsurface environments, and strategies capable to mitigate their contamination.

Temporal studies are essential to understand the seasonal variability of MNP concentrations in groundwater, particularly in regions with significant agricultural runoff. Monitoring programs should integrate data on precipitation, groundwater recharge rates, and agricultural practices to elucidate patterns of contamination and transport dynamics, therefore advancing on aspects related to hydrogeological and environmental influencing micro(nano)plastics distribution

The co-existence of MNPs with nutrients (and their transformation products; NO₃- and PO₄3-) requires detailed investigation. Studies should focus on how these contaminants adsorb onto MNPs, particularly nanoplastics, and the subsequent effects on their mobility, bioavailability, and toxicity. The role of aging processes in enhancing the sorption capacity of MNPs should also be prioritized. Their interactions with herbicides, pesticides, and salts, seem to be more advanced. Research on the impacts of MNPs on subterranean biota is critically lacking. Laboratory and field-based studies should evaluate the chronic toxicity of MNPs and their role as carriers of agrochemicals, considering groundwater-specific conditions such as low oxygen levels, high pressure, and limited microbial diversity. Test organisms should include those representative of groundwater ecosystems, such as stygobitic species, to provide ecologically relevant insights.

By advancing the understanding of MNP behavior in groundwater systems and developing effective mitigation strategies, future research can safeguard this vital resource against the emerging threat of plastic pollution.

Final Considerations

This review consolidates current knowledge on the occurrence, distribution, and risks associated with micro- and nanoplastics in groundwater systems, particularly in agricultural settings. Agricultural activities have been identified as major contributors to plastic particles contamination, with primary sources including plastic mulching films, pesticide containers, fertilizer bags, and greenhouse materials. The predominance of nanoplastics in groundwater, driven by their enhanced mobility and sorption properties, underscores their potential for deeper infiltration and prolonged environmental persistence.

The literature review considerable spatial and temporal variability in micro- and nanoplastics concentrations, formats, and polymer types across groundwater systems, influenced by factors such as land use, atmospheric deposition, surface water intrusion, and the characteristics of the vadose zone. Nanoplastics were notably smaller in size (average of 774 ± 1367 nm), with fibers and fragments representing the most prevalent particle formats. Common polymers detected include polyethylene, polypropylene, and polyethylene terephthalate, with differences in abundance influenced by their physicochemical properties and environmental degradation rates.

Environmental and hydrogeological parameters such as precipitation, groundwater flow velocity, polymer density, soil characteristics, and groundwater composition (e.g.: turbidity, salinity, nitrate content) significantly influence micro- and nanoplastics distribution and transport dynamics. Seasonal differences also play a role, with some studies reporting higher plastic particles concentrations in the rainy season due to increased infiltration, while others suggest dilution effects during high-precipitation periods.

Despite generally low concentrations in groundwater compared to surface water, the potential of micro- and nanoplastics for ecological harm remains significant. Nanoplastics, in particular, exhibit higher sorption capacities and bioavailability, serving as vectors for co-contaminants such as pesticides, herbicides, salts, and heavy metals.

This review also highlights important methodological considerations, including the need for standardized sampling and analytical protocols to improve data comparability. Current limitations in sample volume and particle size may underestimate the true prevalence and risks posed by nanoplastics in subsurface environments.

Altogether, the findings underscore the emerging threat of micro- and nanoplastics in groundwater systems and the necessity for target research to understand their long-term environmental and health implications. A comprehensive understanding of their behavior and interactions is essential for informing risk assessments, regulatory policies, and the development of mitigation strategies to protect groundwater resources in agricultural landscapes.

SUPPLEMENTARY MATERIAL

Table SI.

Acknowledgements

This research was funded by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), the National Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), and the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG).

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HEEREY L, O’SULLIVAN JJ, BRUEN M, TURNER J, MAHON AM, MURPHY S, LALLY HT, O’CONNOR JD, O’CONNOR I & NASH R. 2023. Export pathways of biosolid derived microplastics in soil systems – Findings from a temperate maritime climate. Sci Total Environ 888: 164028.
HUANG Y, LIU Q, JIA W, YAN C & WANG J. 2020. Agricultural plastic mulching as a source of microplastics in the terrestrial environment. Environ Pollut 260: 114096.
JASECHKO S & PERRONE D. 2021. Global groundwater wells at risk of running dry. Science 372(6540): 418-421.
JEONG E, KIM Y-I, LEE J-Y & RAZA M. 2023. Microplastic contamination in groundwater of rural area, eastern part of Korea. Sci Total Environ 895: 165006.
KIM Y-I, JEONG E, LEE J-Y, CHIA RW & RAZA M. 2023. Microplastic contamination in groundwater on a volcanic Jeju Island of Korea. Environ Res 226: 115682.
KWIATKOWSKA K & ORMANIEC P. 2024. Microbial Succession on Microplastics in Wastewater Treatment Plants: Exploring the Complexities of Microplastic-Microbiome Interactions. Microb Ecol 87(1): 105.
LI H, WANG F, LI J, DENG S & ZHANG S. 2021. Adsorption of three pesticides on polyethylene microplastics in aqueous solutions: Kinetics, isotherms, thermodynamics, and molecular dynamics simulation. Chemosphere 264: 128556.
LI Y, XIA X, ZHANG J, LIN X, ZHANG Y, WANG H, LI Y, ZHANG Q & ZHANG S. 2023. Bioavailability of micro/nanoplastics and their associated polycyclic aromatic hydrocarbons to Daphnia Magna: Role of ingestion and egestion of plastics. Sci Total Environ 890: 164171.
LIU Y, SHAO H, LIU J, CAO R, SHANG E, LIU S & LI Y. 2021. Transport and transformation of microplastics and nanoplastics in the soil environment: A critical review. Soil Use Manage 37(2): 224-242.
MACHENDIRANATHAN M, JIN G, HUANG H, LIANG T, LIN Z, LIN H, XIE L & CHEN F. 2024. Vertical distribution of microplastics in coastal sediments of Xuwen Coral Reef National Nature Reserve, China. J Oceanol Limnol 43: 422-432.
MU H, WANG Y, ZHANG H, GUO F, LI A, ZHANG S, LIU S & LIU T. 2022. High abundance of microplastics in groundwater in Jiaodong Peninsula, China. Sci Total Environ 839: 156318.
NATH S, ENERIJIOFI KE, ASTAPATI A & GUHA A. 2024. Microplastics and nanoplastics in soil: Sources, impacts, and solutions for soil health and environmental sustainability. J Environ Qual 53(6): 1048-1072.
O’CONNOR D, PAN S, SHEN Z, SONG Y, JIN Y, WU W-M & HOU D. 2019. Microplastics undergo accelerated vertical migration in sand soil due to small size and wet-dry cycles. Environ Pollut 249: 527-534.
PENCIK O, DURDAKOVA M, MOLNAROVA K, KUCSERA A, KLOFAC D, KOLACKOVA M, ADAM V & HUSKA D. 2023. Microplastics and nanoplastics toxicity assays: A revision towards to environmental-relevance in water environment. J Hazard Mater 454: 131476.
PINASSEAU L, WIEST L, VOLATIER L, MERMILLOD-BLONDIN F & VULLIET E. 2020. Emerging polar pollutants in groundwater: Potential impact of urban stormwater infiltration practices. Environ Pollut 266: 115387.
PUCKOWSKI A, CWIĘK W, MIODUSZEWSKA K, STEPNOWSKI P & BIAŁK-BIELIŃSKA A. 2021. Sorption of pharmaceuticals on the surface of microplastics. Chemosphere 263: 127976.
REN Z, GUI X, XU X, ZHAO L, QIU H & CAO X. 2021. Microplastics in the soil-groundwater environment: Aging, migration, and co-transport of contaminants – A critical review. J Hazard Mater 419: 126455.
SAMANDRA S, JOHNSTON JM, JAEGER JE, SYMONS B, XIE S, CURRELL M, ELLIS AV & CLARKE BO. 2022. Microplastic contamination of an unconfined groundwater aquifer in Victoria, Australia. Sci Total Environ 802: 149727.
SEVERINI E, DUCCI L, SUTTI A, ROBOTTOM S, SUTTI S & CELICO F. 2022. River–Groundwater Interaction and Recharge Effects on Microplastics Contamination of Groundwater in Confined Alluvial Aquifers. Water 14(12): 1913.
SHI C, LIU Z, YU B, ZHANG Y, YANG H, HAN Y, WANG B, LIU Z & ZHANG H. 2024. Emergence of nanoplastics in the aquatic environment and possible impacts on aquatic organisms. Sci Total Environ 906: 167404.
SHU X, XU L, YANG M, QIN Z, ZHANG Q & ZHANG L. 2023. Spatial distribution characteristics and migration of microplastics in surface water, groundwater and sediment in karst areas: The case of Yulong River in Guilin, Southwest China. Sci Total Environ 868: 161578.
SLAVEYKOVA VI & MARELJA M. 2023. Progress in Research on the Bioavailability and Toxicity of Nanoplastics to Freshwater Plankton. Microplastics 2(4): 389-410.
STAPLETON MJ, ANSARI AJ & HAI FI. 2023. Antibiotic sorption onto microplastics in water: A critical review of the factors, mechanisms and implications. Water Res 233: 119790.
TIAN L, JINJIN C, JI R, MA Y & YU X. 2022. Microplastics in agricultural soils: sources, effects, and their fate. Current Opinion in Environmental Science & Health 25: 100311.
VIAROLI S, LANCIA M & RE V. 2022. Microplastics contamination of groundwater: Current evidence and future perspectives. A review. Sci Total Environ 824: 153851.
WEI Z, WEI T, CHEN Y, ZHOU R, ZHANG L & ZHONG S. 2024. Seasonal dynamics and typology of microplastic pollution in Huixian karst wetland groundwater: Implications for ecosystem health. J Environ Manage 358: 120882.
XING Y, ZHU X, HUANG J, NAN Y, DUAN Y & ZHANG J. 2024. Toxic effects of microplastics and nitrite exposure on intestinal histology, digestion, immunity, and microbial community of shrimp Litopenaeus vannamei. Mar Pollut Bull 200: 116077.
YU F, YANG C, ZHU Z, BAI X & MA J. 2019. Adsorption behavior of organic pollutants and metals on micro/nanoplastics in the aquatic environment. Sci Total Environ 694: 133643.
ZENG Z, JIA B, LIU X, CHEN L, ZHANG P, QING T & FENG B. 2024 Adsorption behavior of triazine pesticides on polystyrene microplastics aging with different processes in natural environment. Environ Pollut 356: 124319.
ZHANG Q, XU P, YAN N, REN Y, LIANG X & GUO X. 2024. Adsorption of neonicotinoid insecticides by mulch film-derived microplastics and their combined toxicity. Sci Total Environ 955: 177238.
ZOCCHI M & SOMMARUGA R. 2019. Microplastics modify the toxicity of glyphosate on Daphnia magna. Sci Total Environ 697: 134194.

Publication Dates

Publication in this collection
05 Sept 2025
Date of issue
2025

History

Received
28 Nov 2024
Accepted
4 May 2025

This is an open-access article distributed under the terms of the Creative Commons Attribution License

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[19] GUO X, LIU Y & WANG J. 2019. Sorption of sulfamethazine onto different types of microplastics: A combined experimental and molecular dynamics simulation study. Mar Pollut Bull 145: 547-554.

[20] HASSAN F, PRASETYA KD, HANUN JN, BUI HM, RAJENDRAN S, KATARIA N, KHOO KS, WANG Y-F, YOU S-J & JIANG J-J. 2023. Microplastic contamination in sewage sludge: Abundance, characteristics, and impacts on the environment and human health. Environ Technol Innovation 31: 103176.

[21] HE Y-Q, MCDONOUGH LK, ZAINAB SM, GUO Z-F, CHEN C & XU Y-Y. 2024. Microplastic accumulation in groundwater: Data-scaled insights and future research. Water Res 258: 121808.

[22] HEEREY L, O’SULLIVAN JJ, BRUEN M, TURNER J, MAHON AM, MURPHY S, LALLY HT, O’CONNOR JD, O’CONNOR I & NASH R. 2023. Export pathways of biosolid derived microplastics in soil systems – Findings from a temperate maritime climate. Sci Total Environ 888: 164028.

[23] HUANG Y, LIU Q, JIA W, YAN C & WANG J. 2020. Agricultural plastic mulching as a source of microplastics in the terrestrial environment. Environ Pollut 260: 114096.

[24] JASECHKO S & PERRONE D. 2021. Global groundwater wells at risk of running dry. Science 372(6540): 418-421.

[25] JEONG E, KIM Y-I, LEE J-Y & RAZA M. 2023. Microplastic contamination in groundwater of rural area, eastern part of Korea. Sci Total Environ 895: 165006.

[26] KIM Y-I, JEONG E, LEE J-Y, CHIA RW & RAZA M. 2023. Microplastic contamination in groundwater on a volcanic Jeju Island of Korea. Environ Res 226: 115682.

[27] KWIATKOWSKA K & ORMANIEC P. 2024. Microbial Succession on Microplastics in Wastewater Treatment Plants: Exploring the Complexities of Microplastic-Microbiome Interactions. Microb Ecol 87(1): 105.

[28] LI H, WANG F, LI J, DENG S & ZHANG S. 2021. Adsorption of three pesticides on polyethylene microplastics in aqueous solutions: Kinetics, isotherms, thermodynamics, and molecular dynamics simulation. Chemosphere 264: 128556.

[29] LI Y, XIA X, ZHANG J, LIN X, ZHANG Y, WANG H, LI Y, ZHANG Q & ZHANG S. 2023. Bioavailability of micro/nanoplastics and their associated polycyclic aromatic hydrocarbons to Daphnia Magna: Role of ingestion and egestion of plastics. Sci Total Environ 890: 164171.

[30] LIU Y, SHAO H, LIU J, CAO R, SHANG E, LIU S & LI Y. 2021. Transport and transformation of microplastics and nanoplastics in the soil environment: A critical review. Soil Use Manage 37(2): 224-242.

[31] MACHENDIRANATHAN M, JIN G, HUANG H, LIANG T, LIN Z, LIN H, XIE L & CHEN F. 2024. Vertical distribution of microplastics in coastal sediments of Xuwen Coral Reef National Nature Reserve, China. J Oceanol Limnol 43: 422-432.

[32] MU H, WANG Y, ZHANG H, GUO F, LI A, ZHANG S, LIU S & LIU T. 2022. High abundance of microplastics in groundwater in Jiaodong Peninsula, China. Sci Total Environ 839: 156318.

[33] NATH S, ENERIJIOFI KE, ASTAPATI A & GUHA A. 2024. Microplastics and nanoplastics in soil: Sources, impacts, and solutions for soil health and environmental sustainability. J Environ Qual 53(6): 1048-1072.

[34] O’CONNOR D, PAN S, SHEN Z, SONG Y, JIN Y, WU W-M & HOU D. 2019. Microplastics undergo accelerated vertical migration in sand soil due to small size and wet-dry cycles. Environ Pollut 249: 527-534.

[35] PENCIK O, DURDAKOVA M, MOLNAROVA K, KUCSERA A, KLOFAC D, KOLACKOVA M, ADAM V & HUSKA D. 2023. Microplastics and nanoplastics toxicity assays: A revision towards to environmental-relevance in water environment. J Hazard Mater 454: 131476.

[36] PINASSEAU L, WIEST L, VOLATIER L, MERMILLOD-BLONDIN F & VULLIET E. 2020. Emerging polar pollutants in groundwater: Potential impact of urban stormwater infiltration practices. Environ Pollut 266: 115387.

[37] PUCKOWSKI A, CWIĘK W, MIODUSZEWSKA K, STEPNOWSKI P & BIAŁK-BIELIŃSKA A. 2021. Sorption of pharmaceuticals on the surface of microplastics. Chemosphere 263: 127976.

[38] REN Z, GUI X, XU X, ZHAO L, QIU H & CAO X. 2021. Microplastics in the soil-groundwater environment: Aging, migration, and co-transport of contaminants – A critical review. J Hazard Mater 419: 126455.

[39] SAMANDRA S, JOHNSTON JM, JAEGER JE, SYMONS B, XIE S, CURRELL M, ELLIS AV & CLARKE BO. 2022. Microplastic contamination of an unconfined groundwater aquifer in Victoria, Australia. Sci Total Environ 802: 149727.

[40] SEVERINI E, DUCCI L, SUTTI A, ROBOTTOM S, SUTTI S & CELICO F. 2022. River–Groundwater Interaction and Recharge Effects on Microplastics Contamination of Groundwater in Confined Alluvial Aquifers. Water 14(12): 1913.

[41] SHI C, LIU Z, YU B, ZHANG Y, YANG H, HAN Y, WANG B, LIU Z & ZHANG H. 2024. Emergence of nanoplastics in the aquatic environment and possible impacts on aquatic organisms. Sci Total Environ 906: 167404.

[42] SHU X, XU L, YANG M, QIN Z, ZHANG Q & ZHANG L. 2023. Spatial distribution characteristics and migration of microplastics in surface water, groundwater and sediment in karst areas: The case of Yulong River in Guilin, Southwest China. Sci Total Environ 868: 161578.

[43] SLAVEYKOVA VI & MARELJA M. 2023. Progress in Research on the Bioavailability and Toxicity of Nanoplastics to Freshwater Plankton. Microplastics 2(4): 389-410.

[44] STAPLETON MJ, ANSARI AJ & HAI FI. 2023. Antibiotic sorption onto microplastics in water: A critical review of the factors, mechanisms and implications. Water Res 233: 119790.

[45] TIAN L, JINJIN C, JI R, MA Y & YU X. 2022. Microplastics in agricultural soils: sources, effects, and their fate. Current Opinion in Environmental Science & Health 25: 100311.

[46] VIAROLI S, LANCIA M & RE V. 2022. Microplastics contamination of groundwater: Current evidence and future perspectives. A review. Sci Total Environ 824: 153851.

[47] WEI Z, WEI T, CHEN Y, ZHOU R, ZHANG L & ZHONG S. 2024. Seasonal dynamics and typology of microplastic pollution in Huixian karst wetland groundwater: Implications for ecosystem health. J Environ Manage 358: 120882.

[48] XING Y, ZHU X, HUANG J, NAN Y, DUAN Y & ZHANG J. 2024. Toxic effects of microplastics and nitrite exposure on intestinal histology, digestion, immunity, and microbial community of shrimp Litopenaeus vannamei. Mar Pollut Bull 200: 116077.

[49] YU F, YANG C, ZHU Z, BAI X & MA J. 2019. Adsorption behavior of organic pollutants and metals on micro/nanoplastics in the aquatic environment. Sci Total Environ 694: 133643.

[50] ZENG Z, JIA B, LIU X, CHEN L, ZHANG P, QING T & FENG B. 2024 Adsorption behavior of triazine pesticides on polystyrene microplastics aging with different processes in natural environment. Environ Pollut 356: 124319.

[51] ZHANG Q, XU P, YAN N, REN Y, LIANG X & GUO X. 2024. Adsorption of neonicotinoid insecticides by mulch film-derived microplastics and their combined toxicity. Sci Total Environ 955: 177238.

[52] ZOCCHI M & SOMMARUGA R. 2019. Microplastics modify the toxicity of glyphosate on Daphnia magna. Sci Total Environ 697: 134194.